Cassava peel derived self-doped and hierarchical porous carbon as an optimized electrode for the ultra-high energy density of supercapacitor

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The development of advanced electrode materials with optimized properties, including structural morphology, high porosity, and functional group doping, is very important to enhance the energy density of solid-state supercapacitors. Here, a hierarchical 3D porous carbon self-doping obtained from cassava peel through an environmentally benign approach to optimize the supercapacitor working electrode material. The unique sponge-like interconnected pore structure and self-doping features are controlled through chemical impregnation (CIP) of ZnCl2 (CIP/Z), KOH (CIP/K), and H3PO4 (CIP/H) and high-temperature pyrolysis in an N2&CO2 gaseous environment. Furthermore, the optimized CIP/Z carbon material exhibits high content of 94.606 % and a self-doping oxygen heteroatom of about 2.672 %. The unique sponge-like morphology possessed enriches micropores of 94 %, indicating high performance as an electrode material. The electrochemical properties were assessed through a symmetric supercapacitor system assembled in a solid free-binding coin yielding an excellent specific capacitance of 257 F g−1 at 1 A g−1. Meanwhile, the optimized electrode has a high rate capability of 92.43 % and maintained a coulombic efficiency of up to 91.10 % at 10 A g−1. The best working efficiency supercapacitor cell can show a jump in energy density of 35.69 Wh kg−1 at a specific power of 167.68 W kg−1 in an aqueous electrolyte of 1 M H2SO4. These excellent results provide important insights for optimizing electrode materials derived from cassava peel-based porous carbon for symmetrically designed supercapacitors of binder-free solid coins in aqueous electrolytes with high energy density.